1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus incorporated in an optical disk apparatus or the like. The information recording/reproducing apparatus records data on an optical disk comprising a number of zones each having a number of tracks, and reproduces data from the optical disk. When data is recorded in the zones and when it is reproduced from the zones, clock signals having different frequencies corresponding to the respective zones are used.
2. Description of the Related Art
An optical disk is divided into a number of zones each having a number of tracks. In one zone, the number of sectors provided for one track is equal to the number of sectors provided for another track, but the number of sectors provided for each track of one zone differs from the number of sectors provided for each track of another zone. When data is recorded on the optical disk or reproduced therefrom, the optical disk is rotated at a constant speed, and an optical head records or reproduces the data on the basis of clock signals having different frequencies corresponding to the respective zones. The optical head is movable in the radial direction of the optical disk so that data can be recorded on a target track or reproduced therefrom.
An optical disk apparatus employs two PLL (phase locked loop) circuits, one for generating recording clock signals, i.e., timing clocks which are used for data recording, and the other for generating reproducing clock signals, i.e., timing clocks used for data identification when the data read out from the optical disk is reproduced. Each of the recording and reproducing PLL circuits comprises a phase comparator, a filter, and a voltage controlled oscillator (VCO).
However, if the two PLL circuits are incorporated in a single LSI circuit, the voltage controlled oscillators of the PLL circuits may interfere with each other, result in the generation of noise.